1. Field of the Invention:
This invention relates to nuclear steam generators and more particularly to apparatus for remotely repairing the tubes and tubesheet in a nuclear steam generator.
Radioactive contaminants in the primary fluid of a pressurized water nuclear reactor system sometimes deposit on the tubes and in the channel head of the nuclear steam generator causing repair personnel who work within the channel head to be subjected to significant radioactivity. It is desirable to provide an apparatus which can effectively inspect and repair tubes and the associated tubesheet within the steam generator from a remote location so as to reduce the exposure of work personnel to the radiation present within the channel head.
2. Description of the Prior Art:
Copending patent application whose serial number and filing date are respectively Ser. No. 888,701 and Mar. 21, 1978 shows an apparatus similar to the present invention. Such apparatus, however, utilized hydraulic positioning means for moving the apparatus' platform portion relative to the base along a direction known as the Z axis. While the aforementioned apparatus admirably performed the required repair work within the channel head, its hydraulic positioning mechanism lacked the extreme precision and stability which was sometimes necessary for certain specific tool operations. Due to inherent characteristics of two-way hydraulic cylinders, the prior art's positioning mechanism was found to be somewhat slow in one of the two directions of travel.